London by Night - Looking towards St Paul's Cathedral from the South Bank, London
(Canon PowerShot S120
26 mm (in 35 mm full frame equivalent) / 1/20th / f1.8 / ISO 1600
with good use of a wall to lean against!)
Getting Started - # 6 - Showing Your Sensitive Side
We've looked at shutter speed (anything less than 1/100th of a second and be warned that you might get blurring).
And that's just for family pics. In sports you will need to use shutter speeds of 1/1000th and above!
We've looked at aperture - the pupil of your camera lens.
Large f number - say f 32 - means small hole (small pupil) - which stops a lot of light get into your camera - good for bright conditions.
Small f number - say f 2.8 - means large hole (large pupil) - which lets lots of light get into your camera - good for poorly lit conditions.
So now we'll look at the third dancing partner - Sensor Sensitivity - which together with shutter speed and aperture makes the picture happen in the camera.
Camera sensors are to digital cameras what film was to film cameras.
Film came in different 'speeds'. Kodachrome 64 being Kodak's world famous colour slide film - with a speed of 64. I used Kodak Tri-X, a black & white film, which had the - then - electrifying speed of 400!
Camera sensors work in a similar way. A sensor is just an electronic device - with lots of electronic cells on it - which are sensitive to light. The more sensitive to light, the better the sensor can cope with poor lighting conditions.
And sensors have a key advantage over film - and that is you can vary the sensitivity of the sensor at the flick of a switch!
Pretty much all digital camera sensors start their sensitivity at 100. So already we are ahead of Kodachrome 64.
And many camera sensors allow you to then set their sensitivity to a maximum of 3200, 6400, 12800 or even higher.
Speeds that were unthinkable in the days of film.
But this great speed comes at a price.
The higher you set the sensor's sensitivity - say 3200 - the more likely you are to get 'noise' on the image. That is specks will start to appear all over your image, and you will start to lose detail in the picture.
But don't panic, a picture taken at speeds of 800 or 1600 or 3200 - depending on the camera - is more than likely to be good enough for looking at on the back of your phone or on social media.
And, as you might imagine, more expensive cameras are better at keeping the noise - these specks - to a minimum - so top of the range Digital SLRs can take pictures at simply astonishing sensor settings.
But such fantastic performance costs money. So the rest of us live with more affordable models and accept more noise in our photographs.
Much of the time the noise is invisible - or you certainly have to look very closely to see it. And for pictures taken at low sensor speeds of say 100 or 200 or 400 the noise is virtually invisible.
At the 'Getting Started' stage - that's all you need to know. You will soon judge for yourself at what level you regard your pictures as being too noisey. But for typical sensor speeds of 100 to around 800 - you will need to look very closely to see any noise at all.
(Insight - I take a lot of photos in concert / theatre conditions. So it's very low light and the subjects - the actors or singers - move at surprising speed. So I need a camera which has a very sensitive sensor so I can keep the shutter speed quite high (certainly above 1/100th of a second to have a reasonable chance of avoiding blur). My first decent camera was a Fuji Bridge Camera - an excellent learning tool - and as I progressed I reckoned the noise in the snaps from the Fuji were acceptable up to a speed of 800 to 1600. I then, after a few years, moved on to an APS-C / DX sensor sized Nikon DSLR - the D7000 - and with the D7000 I could take pictures at a sensor setting of 1600 to 3200 which were acceptable - certainly for online use. Then, after a few more years, I moved onto a full frame sized sensor, on the Nikon D750 - and with my D750 I can use sensor speeds of 6400 to 10,000 and still get acceptable results. Of course, my Fuji Bridge Camera was much smaller, much lighter & much less expensive than my Nikon D750!)
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